Placebo.

The placebo effect demonstrates the amazing impact the brain can have on physical health. If a patient thinks medicine has been administered to them, by receiving a placebo (a 'fake' tablet or solution) then their symptoms can be alleiviated and the condition healed to some degree. H.K. Beecher looked at 15 different clinical trials of different diseases and found that 35% of the subjects were healed by a placebo alone. However many think they are much less reliable than new treatments, and so it is not a viable process. It also contrasts with the doctor-patient agreement, as it relies on decieit. Whatever the pros and cons of placebos, they are now used in all medical trials. There is argument over their usefullness and effectiveness, but is hard to deny that they have their use.